Lunar eclipse, December 2010

Here is some info pertaining to today’s lunar eclipse.  You can see that the Earth is indeed right between the Sun and the Moon, and that the eclipse will be nicely visible (weather permitting!) from western United States.

1) On the Sun-Earth-Moon positional arrangement:
a) the Sun and Moon declinations are very close to being equal in value and opposite in sign/hemisphere, and,
b) their Greenwich Hour Angles (GHA) differ by 180º, which places the two bodies on opposing meridians.

The Moon is of course 15 days “old” and its phase is “full” (100% of the disc illuminated).

2) On the visibility of the eclipse:
The Moon subpoint (a.k.a. GP = geographical position) is:
Latitude (from declination): N 23º 44.9′ (very close to Tropic of Cancer)
Longitude (from GHA): 124º west of Greenwich
This location in the Pacific Ocean rather close to Baja California makes this eclipse visible from our area.

The Sun is essentially on the Tropic of Capricorn (declination S 23º 26.2′) making this a rare event when an eclipse coincides with a solstice.

The time given is Greenwich time (Universal Time, UT) which is 8 hours ahead of our own Pacific Standard Time.



A picture taken by a friend of this blog:



(first published on December 20, 2010)

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